1. Field of the Invention
The present invention relates to a swash-plate type compressor including a swash-plate accommodated in a swash-plate chamber in a cylinder block and a plurality of reciprocally movable double-headed pistons inserted in the respective working bores in the cylinder block for forming compression chambers on either side of each of the double-headed pistons, and in particular, the present invention relates to an improved shaft-bearing structure in a swash-plate type compressor.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 3-92587, for example, discloses a swash-plate type compressor comprising a cylinder block, a drive shaft supporting a swash-plate and a plurality of double headed pistons arranged in the cylinder block. The cylinder block is formed of a front block half and a rear block half coupled together, and has at the juncture of the front and rear block halves a swash-plate chamber accommodating the swash-plate. The ends of the front and rear block halves are covered by front and rear housings, respectively, via valve plates.
A refrigerating gas to be compressed and containing lubricating oil therein is introduced from the outside conduit to the swash-plate chamber, and from the swash-plate chamber to the compression chambers, via suction passages. The suction passages are formed in the cylinder block between two adjacent working bores. A suction chamber is formed in the central region of the internal space between each of the front and rear housings and each of the valve plates, and a discharge chamber is formed in the peripheral region of the internal space between each of the front and rear housings and each of the valve plates. The suction chamber communicates with the compression chambers via suction valves and the discharge chamber communicates with the compression chambers via discharge valves. The refrigerating gas is introduced from the suction chamber to the compression chambers and discharged from the compression chambers into the discharge chamber, as the pistons reciprocally move.
In the swash-plate type compressor, the working bores are equidistantly arranged on a circle having a center in coincidence with the longitudinal center line of the compressor. The distance between two adjacent working bores is proportional to the radius of the working bore arranging circle; the greater the distance between two adjacent working bores is, the greater the radius of the working bore arranging circle, and the smaller the distance between two adjacent working bores is, the smaller the radius of the working bore arranging circle.
Usually, the distance between two adjacent working bores is sufficiently extended so that the strength of the cylinder block is ensured. The suction passages are formed in the cylinder block between two adjacent working bores, this suction structure causing a decrease in the structure of the cylinder block. Therefore, it is difficult to minimize the radius of the working bore arranging circle and to obtain a compactly designed compressor. Also, the arrangement of the suction passages in the cylinder block causes a reduction in the pressure of the refrigerating gas and the compression ratio decreases.
The drive shaft supporting the swash-plate is supported by a pair of radial bearings and a pair of thrust bearings. That is, the radial load to the drive shaft is supported by the cylinder block via the radial bearings, and the thrust load to the drive shaft is supported by the cylinder block via the thrust bearings. These bearings are lubricated by lubricating oil contained in the refrigerating gas. However, this arrangement in which the radial load and the thrust load are supported by separate bearings needs complex assembly work.